A tile shower drain efficiently manages water by using a two-stage drainage system that handles both surface water and water that seeps through the tile and grout.
Much of the shower water is directed to the drain strainer and evacuated directly into the plumbing system. However, not all water flows directly into the visible drain opening. Tile and grout, while water-resistant, are not perfectly waterproof.
Any residual water that seeps through the grout joints and the supporting mortar bed is captured by a crucial underlying layer: the shower pan membrane. This membrane acts as a waterproof barrier. It rests on a required sloped fill (typically 1/4” per foot) beneath the tile and mortar bed. This slope ensures that the water collected on top of the membrane flows towards the drain assembly.
At the drain assembly, just above the main pipe connection and below the surface tile, are small openings called weep holes. The water collected on the sloped shower pan membrane flows down the slope, enters these weep holes, and is then evacuated to the sewer system, preventing water from being trapped and causing damage or mold issues within the shower structure.
Key Components of a Tile Shower Drain System
Understanding the different layers helps explain how the system works:
- Tile & Grout: The visible surface. While largely directing water, they allow some moisture to pass through.
- Mortar Bed: A layer of mortar beneath the tile that provides support and slope. Water can seep through this layer.
- Shower Pan Membrane: A waterproof layer installed below the mortar bed. It collects water that seeps through the layers above.
- Sloped Fill: A base (often concrete or mortar) sloped towards the drain to direct water on the membrane. Code typically requires a slope of 1/4" per foot.
- Weep Holes: Small holes in the drain assembly located just above the shower pan membrane layer, allowing collected water to enter the drain pipe.
- Drain Strainer: The visible metal cover where most water initially enters.
The Two Drainage Paths
Here's a simple breakdown of the water's journey:
- Primary Path: Shower water flows directly over the tile surface and into the drain strainer, going straight into the main drain pipe.
- Secondary Path: Water seeps through grout and tile -> through the mortar bed -> onto the shower pan membrane -> down the slope of the membrane -> into the weep holes of the drain -> into the drain pipe.
This dual system ensures that water is effectively removed from the shower area, protecting the building structure from moisture damage over time.
